The use of ferrite particles to produce heating in alternating magnetic fields is known in the art. As disclosed in U.S. Pat. No. 3,391,846 to White, and U.S. Pat. No. 3,902,940 to Heller et al., ferrite particles have been used to produce heat in various systems to cause chemical reactions, melt materials, evaporate solvents, produce gases, and for other purposes.
PCT International Publication WO84/02098 (Application No. PCT/US83/01851) corresponding to U.S. Pat. No. 4,914,267 of Derbyshire discloses the use of ferromagnetic materials having the desired Curie temperature in electrically conductive layers to provide auto-regulated heating to the Curie temperature of the material upon application of an alternating current to the conductive layer of ferromagnetic material. The power applied to the ferromagnetic layer is in the form of an alternating current source which produces skin effect or eddy current heating in the continuous ferromagnetic layer. As the ferromagnetic layer reaches the Curie temperature, the permeability of the layer drops and the skin depth increases, thereby spreading the current through the wider area of the ferromagnetic layer until the Curie temperature is achieved throughout and the desired heating is achieved.
In my copending applications referred to above and incorporated herein by reference, I disclose the use of magnetic particles in combination with heat-recoverable articles in an alternating magnetic field systems to effect heating and recovery of the articles. In some instances therein, the heat from the article melts solder preforms present in those articles.
It is also known that soldering can be accomplished by induction heating in a magnetic field. In such induction heating, the magnetic field inductively heats the article or device being soldered and that heat is transferred from the article or device to the solder to flow the solder. For example, see U.S. Pat. No. 4,107,506 to Pelegri.
It is an object of this invention to provide an improved method for soldering which provides for efficient and specific heating of the solder itself.
It is a further object of this invention to provide a self-regulating system for heating to flow solder and thereby reduce the risk of overheating the solder or the device or article being soldered.
Other objects and advantages of this invention will be apparent to one skilled in the art.